Crows Solve Puzzles Inspired by Aesop's Fables

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Crows are famously clever creatures — so much so that the birds'
intelligence was recognized in ancient lore. In the story of "The
Crow and the Pitcher" from Aesop's Fables, a thirsty crow drops
stones into narrow jar to raise the low level of water inside so
he can take a drink.

Now scientists have evidence to back up that tale. New Caledonian
crows actually do understand how to make water displacement work
to their advantage, experiments showed. The results suggest that
the birds
are, at least in some respects, as smart as first-graders,
according to the study.

Researchers, led by Sarah Jelbert at the University of Auckland
in Australia, presented six crows with tubes filled with water.
Inside the tubes, a worm or chunk of meat on a cork was floating,
just out of reach of the crow's beak. [ The
5 Smartest Non-Primates on the Planet ]

In front of the tubes, the researchers arranged a bunch of heavy
rubber erasers that would sink, and light polystyrene objects
that would float. In other variations of the experiment, the
birds were presented with hollow and solid cubes.

The crows figured out that they could drop the heavy objects and
the solid cubes into the tubes in order to raise the water level
and get their snack, the researchers reported March 26 in the
journal
PLOS ONE.

The crows' understanding of water displacement, however, might be
incomplete. The birds fumbled in experiments in which they could
choose to drop objects in either a wide tube or a narrow tube to
retrieve a snack, the researchers said. Dropping objects into the
skinnier tube would lift the water level by a greater amount and
put the treat within reach after just two drops. In contrast, it
took around seven drops to raise the snack to the same level in
the wider tube. The crows apparently didn't realize this, and
most of them went for the wider tube first.

Previous studies showed that chimpanzees and human children can
solve similar tasks. In a 2011 study detailed in
PLOS ONE, apes and kids figured out that they could spit
water into a tube to reach a peanut that was floating in a small
amount of water at the bottom.

"The ability to detect and respond to relevant causal properties
demonstrated here, is striking — in spite of its limits
— and rivals that of 5- to 7-year-old children," the
researchers of the new study wrote.